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首页> 外文期刊>Free Radical Biology and Medicine: The Official Journal of the Oxygen Society >Ni exposure impacts the pool of free Fe and modifies DNA supercoiling via metal-induced oxidative stress in Escherichia coli K-12
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Ni exposure impacts the pool of free Fe and modifies DNA supercoiling via metal-induced oxidative stress in Escherichia coli K-12

机译：镍暴露会影响自由铁库，并通过金属诱导的大肠杆菌K-12中的氧化应激改变DNA超螺旋

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The biology of nickel has been widely studied in mammals because of its carcinogenic properties, whereas few studies have been performed in microorganisms. In the present work, changes accompanying stress caused by nickel were evaluated at the cellular level using RNA-Seq in Escherichia coli K-12. Interestingly, a very large number of genes were found to be deregulated by Ni stress. Iron and oxidative stress homeostasis maintenance were among the most highly enriched functional categories, and genes involved in periplasmic copper efflux were among the most highly upregulated. These results suggest that the deregulation of Fe and Cu homeostatic genes is caused by a release of free Cu and Fe ions in the cell which in turn activate the Cu and Fe homeostatic systems. The content of Cu was not significantly affected upon the addition of Ni to the growth medium, nor were the Cus and CopA Cu-efflux systems important for the survival of bacteria under Ni stress In contrast the addition of Ni slightly decreased the amount of cellular Fe and activated the transcription of Fur regulated genes in a Fur dependent manner. Cu or Fe imbalance together with oxidative stress might affect the structure of DNA. Further experiments revealed that Ni alters the state of DNA folding by causing a relaxed conformation, a phenomenon that is reversible by addition of the antioxidant Tiron or the Fe chelator Dip. The Tiron-reversible DNA relaxation was also observed for Fe and to a lesser extent with Cu but not with Co. DNA supercoiling is well recognized as an integral aspect of gene regulation. Moreover our results show that Ni modifies the expression of several nucleoid-associated proteins (NAPs), important agents of DNA topology and global gene regulation. This is the first report describing the impact of metal-induced oxidative on global regulatory networks. (C) 2016 Elsevier Inc. All rights reserved.
机译：由于镍的致癌特性，因此已在哺乳动物中进行了广泛的研究，而对微生物的研究却很少。在当前的工作中，在大肠杆菌K-12中使用RNA-Seq在细胞水平上评估了由镍引起的伴随压力的变化。有趣的是，发现大量基因被镍胁迫解除调控。铁和氧化应激稳态维持是功能最丰富的功能类别之一，而与周质铜外流有关的基因也是最上调的功能类别。这些结果表明，Fe和Cu稳态基因的失调是由于细胞中游离Cu和Fe离子的释放引起的，而后者又激活了Cu和Fe稳态系统。在生长培养基中添加镍后，铜的含量没有受到显着影响，Cus和CopA铜外排系统对于在Ni胁迫下细菌的存活也并不重要。相反，添加Ni会稍微降低细胞中Fe的含量并以Fur依赖性方式激活Fur调控基因的转录。铜或铁的不平衡以及氧化应激可能会影响DNA的结构。进一步的实验表明，Ni通过引起松弛的构象来改变DNA折叠的状态，这种现象可以通过添加抗氧化剂Tiron或Fe螯合剂Dip来逆转。铁还观察到铁的Tiron可逆DNA弛豫，而Cu却观察到Tiron可逆的DNA弛豫程度较小，而Co则未见。DNA超螺旋被公认为是基因调控的重要方面。此外，我们的结果表明，Ni修饰了几种与核苷酸相关的蛋白质（NAP）的表达，这些蛋白质是DNA拓扑结构和全局基因调控的重要媒介。这是第一份描述金属诱导的氧化剂对全球监管网络的影响的报告。 （C）2016 Elsevier Inc.保留所有权利。

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